NEW 

 ENGLAND 



AUTUMN 



plant plant [ON 



T"^ 



\ 



CHORDARIA 



vj 



SUMMER 



NAPLES 



IRISH 

 SEA 



Fig. 71 Diagram to show different life cycles recorded for 

 Ectocarpus siliculosis from different localities. 



A schema of the Irish sea cycle is seen in Fig. 71. It has been 

 suggested that the differences between the plants from the two 

 locaUties are due to differences in the tides, light conditions or 

 temperature, with perhaps more emphasis on the last. A further 

 study of the NeapoUtan form by Schussnig and Kothbauer (i934) 

 has subsequently revealed the existence of unilocular sporangia, 

 although the products from these did not undergo fusion. The 

 results of this study do not fit in at all satisfactorily with those of 

 Knight because it will be seen that there is a considerable seasonal 

 variation. Yet another study of this species has also been carried 

 out in America by Papenfuss (1935), and his conclusions agree 



131 



